One of the main causes of dementia in elderly patients is Alzheimer's Disease (AD). AD is caused by degeneration in various parts of the brain attributed to loss of brain neurons and synapses. Amyloid fibrils and plaques are commonly found in brains of patients afflicted by AD, and it has been suggested that formation and growth of amyloid plaques are one of the main causes of AD.
Amyloid plaques are formed primarily by the aggregation and accumulation of naturally occurring proteins. One protein, which causes amyloid formation, is termed Amyloid Beta, also known as Beta Amyloid (Aβ). Aβ is a peptide composed of between 40 and 43 amino acids and it exists in humans in both soluble and insoluble forms. In its soluble form, it circulates in plasma and in brain interstitial and cerebrospinal fluids. In its insoluble form, Aβ forms aggregates comprising amyloid fibrils which can form disease-causing amyloid plaques.
In addition to Aβ, other proteins such as amylin, alpha-synuclein, Huntingtin and beta-2 microglobulin have been indicated as causes for amyloid formation.
In addition to AD, other diseases have been associated with accumulation of amyloid plaques including Lewy body dementia, cerebral amyloid angiopathy and inclusion body myositis.